Fan blade assembly

Abstract

The present disclosure relates generally to a fan blade assembly. In an embodiment, the fan blade assembly includes an airfoil having a forward edge covered by a sheath. The airfoil and the sheath are made from dissimilar conductive materials. A sacrificial anode layer is applied to at least a portion of the sheath so that the sacrificial anode layer will corrode instead of the airfoil.

What is claimed is: 
     
       1. A method of forming a fan blade assembly, comprising:
 providing a conductive airfoil; 
 providing a conductive sheath including an outer surface; 
 applying a sacrificial anode layer only on at least a portion of the outer surface of the sheath or only on a portion of the conductive airfoil, wherein the sacrificial anode layer is formulated as a colored composition or colored during application in order to provide a visual corrosion risk indicator; 
 coating the sacrificial anode layer, the conductive airfoil and the conductive sheath with an erosion protection coating, wherein when the sacrificial anode layer wears away the sacrificial anode layer provides a distinct visual indication; 
 wherein the sacrificial anode layer is more anodic than the conductive airfoil; and 
 wherein the conductive airfoil is joined to the sheath and the sacrificial anode layer corrodes instead of the conductive airfoil when a galvanic potential is created between the conductive airfoil and the sheath. 
 
     
     
       2. The method of  claim 1 , wherein the conductive sheath is joined to the conductive airfoil with a nonconductive adhesive. 
     
     
       3. The method of  claim 1 , wherein the conductive airfoil is formed from an aluminum alloy. 
     
     
       4. The method of  claim 1 , wherein the conductive sheath is formed from titanium or titanium alloys. 
     
     
       5. The method of  claim 1 , wherein:
 the conductive airfoil further includes an airfoil forward edge, a pressure side and a suction side; 
 the conductive sheath further includes a sheath head section and first and second flanks extending from the sheath head section; and 
 wherein the conductive sheath covers at least a portion of the airfoil forward edge, the first flank covers at least a portion of the suction side, and the second flank covers at least a portion of the pressure side. 
 
     
     
       6. The method of  claim 1 , wherein the fan blade assembly comprises a portion of a gas turbine engine. 
     
     
       7. The method of  claim 1 , wherein the sacrificial anode layer is disposed on a perimeter of the sheath outer surface at a predetermined sacrificial anode layer width. 
     
     
       8. The method of  claim 7 , wherein the sacrificial anode layer width comprises approximately ¼ inch. 
     
     
       9. The method of  claim 1 , wherein the sacrificial anode layer comprises a material selected from the group consisting of: zinc, zinc alloy, electrochemically active aluminum alloy, magnesium, magnesium alloy, zinc and aluminum alloy, magnesium and aluminum alloy, zinc and magnesium alloys with aluminum, aluminum, cadmium, beryllium and alloys of aluminum, cadmium, and beryllium, and alloys of any of the above. 
     
     
       10. The method of  claim 1 , wherein the galvanic potential difference between the sacrificial anode layer and the conductive airfoil is in absolute values between greater than 0 mV and approximately 2000 mV. 
     
     
       11. The method of  claim 10 , wherein the galvanic potential difference between the sacrificial anode layer and the conductive airfoil is in absolute values between greater than 0 mV and approximately 1000 mV. 
     
     
       12. The method of  claim 1 , wherein the galvanic current density between the sacrificial anode layer and the conductive airfoil is between approximately 1 μA/cm 2  and approximately 10 μA/cm 2 . 
     
     
       13. The method of  claim 1 , wherein the sacrificial anode layer comprises a thickness of approximately 0.001 inch to approximately 0.05 inch. 
     
     
       14. The method of  claim 1 , wherein the sacrificial anode layer comprises a first color different than a second color of the conductive airfoil. 
     
     
       15. The method of  claim 14 , wherein the sacrificial anode layer is disposed on a perimeter of the sheath outer surface at a predetermined sacrificial anode layer width. 
     
     
       16. The method of  claim 14 , wherein the conductive airfoil is formed from an aluminum alloy. 
     
     
       17. The method of  claim 16 , wherein the conductive sheath is formed from titanium or titanium alloys. 
     
     
       18. The method of  claim 17 , wherein the sacrificial anode layer comprises a thickness of approximately 0.001 inch to approximately 0.05 inch. 
     
     
       19. The method of  claim 14 , wherein the sacrificial anode layer comprises a thickness of approximately 0.001 inch to approximately 0.05 inch. 
     
     
       20. The method of  claim 14 , wherein the conductive sheath is joined to the conductive airfoil with a nonconductive adhesive.